The service life of a bearing is reduced by dirt and impurities penetrating into the bearing. The mounting of the bearing on one hand may occur in dirty surroundings, and the bearings may, on the other hand during operation, be subjected to dirt, metal chips, etcetera. At use of bearings in continuous casting machines, in rolling mills, paper making machines, etcetera, the bearings may be highly exposed to different kinds of impurities. This is furthermore putting high demands on maintenance.
Thus a good seal for a bearing in many cases can be most important, on one hand for increasing the service life and on the other hand for reducing the requirement of maintenance.
Known solutions for designing sealed bearings are based on two different principles. A seal can either be assembled on a bearing or be built into the bearing. Embodiments of how a seal is assembled on a bearing is shown e.g. in SE-B-454904 and in SE-B-451 081. The seal in these embodiments is constituted by two cooperating sheet metal rings, whereby at least one of the sheet metal rings is notch joined into the outer race ring, whereas the other is fitted to the inner race ring. This solution however means that the seal will project outside the side planes, which in some cases necessitates modifications of the bearing housing and also of the mounting and dismantling tools, etcetera.
According to the other alternative mentioned above, the seal is built into the bearing. In this case the seal is not projecting from the side surfaces of the bearing. Assembly of the seal inside one of the bearing side surfaces requires space and for this reason the width of the bearing itself has been increased in known solutions. Alternatively, the length of the rollers or the contact angle have been reduced. At a known, sealed bearing, the width of the bearing has been increased as compared to a corresponding unsealed bearing in order to maintain the carrying capacity.
In smaller size bearings, typically less than 200 mm in outer diameter, it is common to provide the sealing member with an attachment portion at first peripheral portion of an annular plate ring with a spring portion arranged for introduction into a groove. The spring, which typically is a bent part of the annular plate ring will keep the sealing member in place. This solution which has been promising for smaller size bearings has not been used for larger size bearings. One reason for this is that the sealing lips of larger size bearing are positioned at a greater distance from the mounting groove and that higher tolerance requirements regarding the position of the built-in sealing member is required. Another reason is that due to the increased requirement of rigidity of the annular plate member need to be thicker, which increases difficulties with forming a spring portion without formation of cracks that may lead to breaking of the annular plate ring.
For mid size sealed self aligning bearing it has been proposed to mount the seal in a radial groove in a first outer race ring, where it is fixed with a locking ring and where the opposite side of the seal engages a tapering surface on the inner race ring. EP 577912 relates to a spherical roller bearing including a built in-sealing member.
Large size self aligning bearings are difficult to seal since these bearings are made for handling large angular misalignments. For using seals in those types of bearings it is necessary to compromise. A typical maximum misalignment for a sealed off spherical roller bearing using conventional technology is 0.5[deg.]
With large size self aligning bearings is intended self aligning bearings having an outer diameter above 500 mm.
A built in seal for a large size self aligning bearings is proposed in WO2006/019347. This type of bearing requires additional space in an axial direction. Further the seal is somewhat sensitive due to the pliable nature of the bellow forming the seal for the bearing.
An object of the invention is to provide a large sealed self aligning bearing, which obviates the need for a bellow as a built-in sealing member.
Another object is to provide a large sealed self aligning bearing, which gives additional space for cages/retainers extending outside of the rolling bodies or which gives more space for the rolling bodies before the ring cage or rolling body interferes with the built-in sealing member. Still another object is to provide a sealed self aligning bearing, which provides an improved seal design for a large size bearing.